In conventional diagnostic imaging, different imaging systems are conventionally used in order to obtain images of different types, even where the same type of radiation source is used for two or more different types of images. Thus, for example, separate computed tomography (CT) and x-ray panoramic systems have been used for obtaining different types of images of the same patient using x-ray exposure.
Combination systems that provide both CT and panoramic x-ray imaging have been proposed. For example, U.S. Pat. No. 6,118,842 entitled “X-RAY IMAGING APPARATUS” to Arai et al. discloses an X-ray imaging apparatus for both CT imaging and panoramic imaging. The apparatus includes an X-ray source, an X-ray detector for detecting X-rays having passed through the subject, and supporting means for supporting the X-ray source and the X-ray detector so that they are spatially opposed to each other across the subject; and mode switching means for switching between a CT mode and a panorama mode. To detect X-rays, only one large area X-ray detector is used. The X-ray imaging apparatus can obtain both types of images by switching modes during the imaging session. However, the proposed imaging apparatus performs both CT and panoramic imaging using only one detector. This requires an expensive detector capable of carrying out both imaging functions in a satisfactory manner. Additionally, in order to provide both image types, the proposed solution of Arai et al. compromises image quality by using a uniform distance between the X-ray source and detector, even though different distances would be more advantageous.
U.S. Pat. No. 7,236,563 entitled “COMBINED PANORAMIC AND COMPUTED TOMOGRAPHY PHOTOGRAPHING APPARATUS” to Sa et al. describes a combination system that allows both CT and panoramic imaging using two separate sensors or detectors. By way of example, FIG. 1 in the present application shows an embodiment of the Sa et al. '563 imaging system, a combined panoramic and CT imaging apparatus 400. The patient or other subject is positioned between an x-ray source part 410 and an x-ray sensor part 420. X-ray sensor part 420 rotates in order to position either a CT sensor 423 or a panoramic sensor 421 for obtaining the exposure. For CT imaging, CT sensor 423 is positioned behind the subject, relative to x-ray source part 410. The operator rotates CT sensor 423 into this position as part of imaging setup. Similarly, the operator rotates panoramic sensor 421 into position behind the subject as part of the setup for a panoramic imaging session.
Another system combines CT, panoramic, and cephalometric imaging from a single apparatus. U.S. Pat. No. 7,424,091 entitled “COMBINED PANORAMIC, CT (COMPUTED TOMOGRAPHY) AND CEPHALOMETRIC PHOTOGRAPHING APPARATUS” to Park et al. describes such a system, shown by way of example in FIG. 2. A combined panoramic, CT, and cephalometric imaging apparatus 300 has similar radiation source and sensor components to the earlier system of FIG. 1 and adds a separate cephalometric imaging part 310, mounted on a separate arm 315.
While both Sa et al. '563 and Park et al. '091 combine these imaging functions, there is room for improvement. One problem common to both systems relates to sensor positioning for each specific type of imaging that is needed. In order to use any of the types of imaging available, the specific sensor type for that imaging must be suitably positioned in the path of exposure radiation. At the same time, the unused sensor or sensors must be moved out of the way, so that they do not obstruct the path of radiation to the appropriate sensor. For example, with respect to the Sa et al. '563 disclosure, panoramic sensor 421 must be either removed or repositioned in order to allow CT imaging; similarly, CT sensor 423 must be removed or repositioned during panoramic imaging. For the three-function device described in the Park et al. '091 disclosure, in order to use the cephalometric imaging function, both panoramic and CT sensors 421 and 423 must be moved out of the way of the radiation path between X-ray source part 410 and cephalometric imaging part 310. In addition, manual attachment of the sensor for cephalometric imaging is required, and other manual repositioning of components appears to be needed in order to perform cephalometric imaging.
Thus, there is a need for a combined imaging apparatus that provides improved mechanisms for positioning detectors for panoramic, CT, and cephalometric imaging.